Lightweight cementitious composite material

ABSTRACT

A lightweight cementitious composite material includes expanded synthetic polymer particulate having a particle size of between 0.0625 and 0.5 inches. A dispersant coating on said particulate suppresses electrostatic attraction between particulate particles. A matrix surrounds the particulate and is present from 0.25 to 1 pound per gallon of dispersant coated particulate.

RELATED APPLICATION

This application claims priority of U.S. Provisional Patent Application60/276,410 filed Mar. 16, 2001 and is incorporated herein by reference.

FIELD OF THE INVENTION

The present invention relates to cementitious composites and, moreparticularly, to polymer particulate filled cementitious compositesparticularly well suited for roofing applications.

BACKGROUND OF THE INVENTION

The preparation of low density concrete incorporating lightweighthydrophilic aggregates such as vermiculite, cork, slag and the like in ahydrophobic matrix such as a cement mixture are well known. The densityand longevity of a cementitious composite are improved through theincorporation of polymeric foam particles, for example, polystyrenefoam, as the lightweight aggregate. However, cementitious material,being hydrophilic, has inadequate adhesion to lightweight polymericaggregates which are hydrophobic while the use of a binding agent in thecement mixture or a pre-coat of the hydrophobic polymeric particles witha binding agent to promote adhesion therebetween has long beencontemplated.

The prior art is replete with binding agents including bituminousproducts, coal tars, mixtures of pitch with polymeric resins, shellac,polyvinyl acetate and the like. Additional additives such as metal ionshave been added to binding agents to lessen the tack of the coatedparticles and lessen coalescence between particles. Prior artlightweight cementitious composites containing hydrophobic polymericparticulate have been limited to certain limitations owing topumpability problems, cost, environmental concerns regarding binderleachants therefrom, and particle aggregation during mixing andapplication. Additionally, drying time of prior art composites issufficiently long that such composites are susceptible to overnightwashout before set. Thus, there exists a need for a lightweightcementitious composite material that addresses many of theselimitations.

SUMMARY OF THE INVENTION

A lightweight cementitious composite material includes expandedsynthetic polymer particulate having a particle size of between 0.0625and 0.5 inches. A dispersant coating on said particulate suppresseselectrostatic attraction between particulate particles. A matrixsurrounds the particulate and is present from 0.25 to 1 pound per gallonof dispersant coated particulate. A process of applying a compositematerial to a substrate comprises the steps of: forcing a stream ofdispersant into fluid communication with a stream of expanded syntheticpolymer particulate having a particle size between 0.0625 and 0.5 inchesto form a dispersed particulate; propelling said dispersed particulateand a matrix slurry through a tube to form a foamed combined streamwhere the matrix is present from 0.25 to 1 pound of said matrix pergallon of said dispersed particulate; and applying said foamed combinedstream to the substrate.

A process for preparing a lightweight structure includes passing anexpanded synthetic polymer through a plurality of meshes to remove afraction therefrom having dimensions of less than 0.0625 inches andgreater than 0.5 inches to obtain an expanded synthetic polymerparticulate. A dispersion is then mixed with the expanded syntheticpolymer particulate to form a lightweight dispersal. The dispersal iscombined with a matrix at a ratio of between 0.25 to 1 pound of thematrix per gallon of dispersal. After the dispersal and the binder arecombined, sufficient time is allowed for the matrix to set.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

The present invention has utility in the formation of lightweightcementitious composite materials that contain recycled synthetic polymerparticulate and are operative in construction settings. The presentinvention finds uses in roofing materials, structural coatings, andconstruction panel fabrication.

The present invention has been developed around the appreciation thatdifferent sized synthetic polymer particulate is productively used toform coatings and structures that meet handling and performanceexpectations for such structures.

An expanded synthetic polymer is formed to a particle size of between0.0625 and 0.5 inches. Preferably, the synthetic polymer is obtained bygrinding waste material. More preferably, the particle size is between0.125 to 0.375 inches. A ground material is sieved to remove particlesizes outside of this particle range. It is appreciated that excessivelylarge particles outside of the aforementioned particle size range areoptionally returned to a regrind process. In an effort to utilizeparticles separated during the particle preparation process that aresmaller than 0.0625 inches, these smaller particle can be used to addvolume to an inventive reinforcement slurry. The invention is alsodeveloped around the fact that densities, compression strength,insulation values, and composition weights can be adjusted by regulatingthe particle size. For instance, steel decks for some structures mayrequire a lightweight concrete to fill the spaces between the highportion of the deck sheets (flukes) and above highs to impart structuralreinforcement. The required density may exceed that of the lighter largeparticle insulation formulation. It is possible to meet the structuralrequirements then change particle size and slurry ratios to achieve theR-value requirements and not exceed weight restrictions. Then anentirely different ratio of slurry to small particle size can be used toprovide shear to the low density insulation material to give it therequired surface compression strength. The synthetic polymer particulateoperative herein is a hydrophobic expanded material illustrativelyincluding polystyrene, polyisocyanurate, polypropylene, polyethylene,other polyalkylenes and polyurethanes. Preferably, the synthetic polymeris polystyrene. As a result of synthetic polymer particulate grindingand sieving, electrostatic attractions develop therebetween.

A dispersant coating operative herein to suppress electrostaticattraction between synthetic polymer particulate particles includes awide variety of materials. A dispersant coating substance operativeherein illustratively includes slack lime; magnesium oxide; nonionicasphalt roof emulsion; cationic or anionic asphalt emulsions, such as aroad emulsion; ionic styrene butadiene rubber emulsions; neoprenecontaining emulsions; and combinations thereof. It is preferred that anasphalt emulsion is modified with a like pH modifier, such as a rubberfor use herein. Additionally, particulate dispersing coatings are alsooperative to suppress electrostatic attraction between synthetic polymerparticulate. Powder type dispersing coatings operative hereinillustratively include water insoluble carbonates, carboxylic acidsalts, oxides and mixed oxides of metals from periodic table groups II,III and/or IV, and specifically include calcium carbonate, magnesiumcarbonate, barium carbonate, zinc carbonate, magnesium stearate, calciumpalmitate, zinc stearate, aluminum stearate, zinc oxide, aluminum oxide,titanium dioxide, silicon dioxide, magnesium silicate, calcium silicate,aluminum silicate, and combinations thereof; insoluble hydroxides suchas magnesium hydroxide, calcium hydroxide; magnesium phosphate, fumedsilica, type F fly ash; type C fly ash; aluminum sulfate and otherinsoluble sulfates; and combinations thereof. Preferably, powderdispersing agent only lacks water to create a reactive dispersal.Organic polymeric dispersants operative herein illustratively include acopolymer of polyvinyl chloride with other authentically unsaturatedmonomers such as vinyl acetate or vinyl alcohol; acrylic resins;polyimides; epoxy resins and ionic detergents.

Owing to the comparative particulate size difference and lack of smallersynthetic polymer particulate amounting to dust, the amount of thecomparatively expensive dispersant coating required herein is therebydiminished. Preferably, the dispersant coating is present from 0.125 to0.75 pounds per gallon of synthetic polymer particulate. Morepreferably, the dispersant coating material is present from 0.125 to0.50 pounds per gallon of synthetic polymer particulate.

A cementitious matrix material surrounds the dispersed particulate. Thematrix material is present from 0.25 to 1 pound per gallon of dispersedparticulate. Matrix materials operative herein are those conventional tothe art. These illustratively include magnesium oxy-chloride/oxy-sulfate(Sorrel cement) cement, magnesium sulfa alumina cement, magnesiumoxy-phosphate cement, silicate cement and polymer modified Portlandcement. More preferably, the cementitious matrix material is presentfrom 0.3 to 0.8 pounds of activated matrix material per gallon ofdispersed particulate.

Preferably, magnesium oxy-chloride or magnesium oxy-sulfate cement ismixed with 10% by weight of the base matrix material of sulfa aluminacement in instances where rapid setting is desired. Dry silica orsilicate, talc and combinations thereof from 0 up to about 10 weightpercent of the base matrix material to form a cementitious matrix ofexceptional strength compared to a base magnesium oxy-chloride ormagnesium oxy-sulfate cement. A factory prefabricated sheet is operativeherein to lessen washout of material associated with rain contactingcement with 12 hours of application. Preferably, the sheet material is awoven polyester mesh. A sheet material is treated on a first side withabout 0.25 to 0.5 inches of a cementious matrix material. Preferably,the cementious matrix material is magnesium oxy-chloride cement. Thesecond side of the sheet is coated with a water imperious material.Optionally, a fiber reinforcement additive is mixed with either thecementitious matrix or water impervious material. Preferably, the waterimpervious material is roof asphalt containing SBR latex rubber andclay. More preferably, the water impervious material is applied to thesheet material before the cementitious material. In usage, an inventivecomposite material is applied to a roof substrate. The compositematerial being comparatively rich in particulate, preferably, between0.25 and 0.50 pounds of matrix material per gallon of particulate. Theinventive composite is then wetted and overlayered by the cement coatedfirst side of the sheet material that sets to the underlying inventivecomposite material. During the set, the sheet material being coated onthe second side and interpenetrated by the water impervious materialserves to protect the setting cementious matrix from washout.

The process of applying a dispersing coating to the expanded syntheticpolymer particulate according to the present invention is appreciated tobe largely dependent upon a form of the dispersant material used to formthe dispersant coating. Regardless of the method by which a dispersantcoating is applied, the particulate dispersal should be dried to form afree-flowing mass. Preferably, dispersal dehydration is coupled withtumbling to prevent particulate from agglomerating prior to addition ofthe matrix material. It is appreciated that heated air is operative toexpedite drying time. Thus, for example, a basic sodium silicate orpotassium silicate solution is applied at 0.25 pounds of sodium silicatesolution per gallon of particulate is applied. The sodium silicatesolution has a viscosity of less than three times the viscosity ofwater. Upon application of heated air, particulate so coated with asilicate solution is readily dehydrated and stored in a dehumidifiedenvironment for up to several months prior to usage. Optionally, asurfactant is included in the silicate solution in order to promoteparticulate wetability.

Upon forming a dry particulate dispersal, the preferred method ofdelivering the dispersal to for instance a roof is by way of a hose.Particulate dispersal is readily propelled by compressed or mechanicallyblown air. The particulate dispersal is optionally blown through a highhose in a dry condition when a fast setting matrix material is utilizedin combination therewith. The particulate dispersal can then be mixedwith fast setting matrix materials and an inline mixing tube such asthat disclosed in U.S. Pat. No. 4,272,935. Such fast setting matrixmaterials are appreciated to be readily deliverable with airless pump byway of an appropriately sized hose relative to the particulate dispersaldelivery hose. It is appreciated that a catalyst is optionally added tothe matrix material mixture in a small mixing tube located upstream fromthe matrix material-particulate dispersal mixing tube by way of anadditional line or inline reservoir with portion metering capabilities.The metering of the various components is adjusted such that thecombined components are extruded immediately downstream from the mixingtube. An inventive composite material upon being blown onto a substrateis appreciated in most instances to require compaction in smoothing toform suitable. It is appreciated that a composite material prior tomatrix material setting is also optionally poured into molds orotherwise formed into sheets and predetermined structures.

Optionally, a matrix material thickener is provided to adjust theviscosity thereof to facilitate ease of handling and application.Thickeners illustratively includes starch, cellulose, polyacrylate, andlatex.

The present invention is further described with respect to certainnon-limiting examples.

EXAMPLE 1 Expanded Polystyrene Particulate Dispersal Formation

A pH 10 or higher sodium silicate solution is combined with 3% by totalvolume of dibasic esters, the dibasic esters adipate, glutarate andsuccinate as sold by DuPont. Propylene carbonate is added thereto to a3% total weight percent to function as a matrix material. 0.25 to 0.75pounds of resulting solution is combined with a gallon of polystyreneparticles having a particle size between 0.25 and 0.375 inches. Throughhigh shear mixing to homogeneity, particulate dispersal is formed. Thisexample is repeated to give a comparable product with like amounts ofethylene carbonate, monoacitin, diactin or triacitin substitutedtherefor. This formulation is particularly well suited in producing aprefabricated insulation board manufactured in a factory setting.

EXAMPLE 2 Roofing Fabric-foam Particulate Dispersal

0.4 pounds of pH adjusted SBR modified anionic asphalt is mixed with onegallon of expanded polyurethane particulate. The resulting fast settingasphalt emulsion is tumbled dry while mixing untreated ⅛ inch andsmaller particulate and powder dispersing agents with care taken toavoid premature compaction thereof, and applied at room temperature andcompacted to form a void fill for re-roofing applications. The SBR latexbeing present at 3 to 9 weight percent of said asphalt emulsion. Theresulting preset composite material is spread smooth in a mound withinan area using a wet trowel within an area that has been brushed, rolled,or sprayed with fast setting rubberized road emulsion. The mound is thencompacted smooth to a consistent density and level in preparation for areinforcement slurry applied thickly to one side of a polyester fabric.This material is readily applied at a 0.25 inch thick layer on the backof a polyester fabric and placed composite material side down onto asubstrate. With the polyester fabric being cut to have approximately asix inch border there around absent composite material. Grooming of thepolyester fabric. A water proofing or roof system is then optionallyoverlayered.

EXAMPLE 3 Precoated Roofing Sheet

A polyester fabric is precoated with a 0.0625 inch thick coat of cementcontaining the particulate dispersal of Example 1. A polyester fabrichas a 10 wet mill coat of elastomeric roof coating or rubberized roofemulsion. The opposite side of this sheet is spray coated with a 10 wetmill layer of magnesium oxy-cement with no particulate dispersal. Thisportion of the process is done in a factory setting. After drying, thissheet can be rolled up for easy installment later. This sheet is used toreinforce the void fill or fill insulation system, resulting in predried layer ready for a roof system. This polyester fabric is thenapplied to a fresh layer of like magnesium oxy-cement on a roofsubstrate such that water runs off without washing away the cement priorto set.

EXAMPLE 4 Roofing Shingles

A magnesium oxy-chloride based cement is mixed with particulatedispersal per one gallon matrix material is applied per gallon of ⅛ inchand smaller particulate and is cast into an 8 foot by 22 inches moldtapering from a ⅛ inch top to ⅝ inch bottom and allowed to set. The setcomposite is reinforced with polyester fabric, using magnesiumoxy-cement, or polymeric resin melt upon removal from the mold. The setcomposite material is cut to desired widths to form roofing shingles orsiding panels. The resulting shingles or panels are suitable for coatingand texturing in a factory setting to yield a finished product.

EXAMPLE 5 Insulation Panels

A magnesium oxy-chloride based cement is mixed with particulatedispersal per one gallon matrix material is applied per gallon of ⅛ inchand smaller particulate. The material is spray applied to an extrudedpolystyrene insulation panel. Spray of the composite material overinsulation boards including seams serves to limit board thermalexpansion associated with temperature change. The particulate isoptionally compacted to densify the particulate.

EXAMPLE 6 Roof Insulation Board

The final mixture of Example 1 is extruded to form a 4 foot wide by 1inch board and allowed to set. Then the resulting board is reinforced onthe surface with a styrene melt to 20 mils.

All patents recited herein are indicative of the level of skill in theart. These patents are hereby incorporated by reference to the sameextent as if each was specifically and individually incorporated byreference.

It is appreciated that one skilled in the art upon understanding theabove detailed invention, that various changes and modifications arereadily made thereto without departing from the scope of the inventionas defined by the appended claims.

What is claimed is:
 1. A structure produced from a composite material comprising: an expanded synthetic polymer particulate having a particle size between 0.0625 and 0.5 inches; a dispersant coating of polyvinyl alcohol on said particulate so as to suppress electrostatic attraction therein; a matrix material of magnesium oxy-chloride cement surrounding said particulate, said matrix material is present from 0.25 to 1 pound per gallon of said particulate.
 2. The structure of claim 1 further comprising a sheet material adjacent to the composition.
 3. The structure of claim 2 wherein said sheet material is polyester.
 4. The structure of claim 2 wherein said sheet material has a first side pre-impregnated with a dry cementious matrix material and a second side pre-impregnated with water impervious material.
 5. The structure of claim 4 wherein said dry cementious matrix material is in contact with the composite material.
 6. The structure of claim 4 wherein said dry cementious matrix is magnesium oxy-chloride cement.
 7. The structure of claim 4 wherein said sheet material is polyester mesh.
 8. The structure of claim 4 wherein said water impervious material is latex rubber modified asphalt emulsion.
 9. The structure of claim 1 wherein said composite further comprises a thickener.
 10. The structure of claim 9 wherein said thickener is cellulose.
 11. The structure of claim 1 wherein the particle size is between 0.1250 and 0.375 inches.
 12. The structure of claim 1 wherein said dispersant is present from 0.125 to 0.75 pounds per gallon of said synthetic polymer particulate.
 13. The structure of claim 1 wherein said matrix material being present from 0.3 to 0.8 pound per gallon of said particulate. 